(not that i have full knowledge of japanese visa issues nor do i know for sure...)

but "Shore Pass" for up to 72 hours are granted to visa-required passport holders when requested by airline/crew/airport administration normally during irregular operations. i guess it all still depends on the immigration officer. (had this happen to a friend on non-visa-exempt passport and me on US passport taking a VDB, the airline personnel had to walk with my friend through immigration, although that was also two years ago).

Since the OP is going in jan, there is plenty of time, and transit visa is fairly cheap when completed in the usa. (isn't it only $10 or so?) I would just get it done now.